Circuit arrangement for adjusting the position of a movable member

ABSTRACT

The present circuit arrangement for adjusting a movable member, for example, for controlling the movement of a chucking head in a hydraulically driven material testing apparatus, comprises two serially arranged comparing stages in which actual and rated values are compared, whereby the output value of the first comparing stage is supplied as a rated value to one input of the next comparing stage the output of which regulates an adjustment control member such as a servo value whereby the movement of the movable member is stopped in response to a second actual value reaching or exceeding a second adjustable rated value.

Wawra et al.

[111 3,800,589 [451 Apr.2, 1974 CIRCUIT ARRANGEMENT FOR ADJUSTING THEPOSITION OF A MOVABLE MEMBER [75] Inventors: Carl Martin Wawra,

Bensheim-Auerbach; Ivan Chudey, Ober-Ramstadt, both of Germany [73]Finona Carl Schenck Assignee:

Maschinenfabrik GmbII, Darmstadt,

Germany Filed: Mar. 27, 1972 Appl. No.: 238,579

[30] Foreign Application Priority Data Mar. 20, 1972 Germany 2213436Int. Cl.

References Cited UNITED STATES PATENTS to H AMPLIFIER Meyer 73/90Weyland et al 73/89 OTHER PUBLICATIONS Pelloux etaL, Review ofScientific Instruments, Vol. 35, No. ll, Nov. 1964, pp, 1564-1567.

Primary Examiner-Charles A. Ruehl Attorney, Agent, or FirmW. G. Fasse[57] ABSTRACT The present circuit arrangement for adjusting a movablemember, for example, for controlling the movement of a chucking head ina hydraulically driven material testing apparatus, comprises twoserially arranged comparing stages in which actual and rated values arecompared, whereby the output value of the first comparing stage issupplied as a rated value to one input of the next comparing stagetheoutput of which regulates an adjustment control member such as aservo value whereby the movement of the movable member is stopped inresponse to a second actual value reaching or exceeding a secondadjustable rated value.

5 Claims, 2 Drawing Figures l IDISPLACEMENT Si i U ,SENSOR Y PARATOR ElFORCE SENSOR 1' CIRCUIT ARRANGEMENT FOR ADJUSTING THE POSITION OF AMOVABLE MEMBER BACKGROUND OF THE INVENTION The present invention relatesto a circuit arrangement for adjusting the position of a movable member,especially for material testing apparatus, such as a hydraulicallydriven testing machine. The present circuit arrangement monitors themovement of a movable member, for example, the chucking head in responseto a predetermined rated value which may represent a displacement ofthemovable member or a force applied to the movable member. The presentcircuit arrangement is, for example, suitable for positioning themovable chucking head of a testing apparatus relative to the length ofthe probe to be tested.

In prior art testing machines, the material probe to be tested isusually chucked first only in one chucking head and thereafter the othermovable chucking head is adjusted in such a manner that the probe mayalso be chucked in the other chucking head. This adjustment of the otheror movable chucking head is accomplished as. a displacement regulationcontrol. However, such adjustment is rather time consuming and requires,especially in connection with delicate probes, a substantial experienceon the part of the operator because in connection with the displacementcontrol large forces may occur rapidly. Such forces may destroy theprobe and damage the testing apparatus whereby even the operatingpersonnel may be endangered. For example, the rated load of the testingapparatus may already be reached in connection with a rigid probe ifduring the adjustment of the spacing between the chucking head and theprobe the chucking head has been moved by five millimeters too farwhereby the probe may become tilted and/or the chucking head may bebent.

OBJECTS OF THE INVENTION In view of the above, it is the aim of theinvention to achieve the following objects, singly or in combination:

tov overcome the above outlined drawbacks of the prior art by making theadjustment of the movable member more sensitive; I

to improve the displacement control for the adjustment of the movablechucking head to the length of the probe in such a manner that damagesto the probe or to the chucking heads themselves are avoided; and

to move the movable member, for example, through a piston rod to apredetermined position in response to the breaking or destruction of theprobe.

SUMMARY OF THE INVENTION According to the invention there is provided acircuit arrangement for adjusting the position of a movable member insuch a manner that the controlled movement in response to a first ratedvalue is stopped when a second actual value reaches or exceeds a secondadjustable rated value whereby the actual values as well as the ratedvalues may be represented by electricalsignals produced by sensing meansin response to a displacement of the movable member or in response to aforce applied to the movable member.

According to one embodiment of the invention there are provided. twocomparing control or regulating means. When the movable member, forexample, the

chucking head ofa material testing apparatus is adjusted a'first actualvalue and a first rated value are compared in the first regulatingcomparing device and a limiting circuit is arranged between the twocomparing devices whereby to supply the output value of the firstcomparing device to a rated value input of the second. comparingregulating device and whereby the second rated value is supplied to saidlimiter to determine the size of the pass range of said limiter circuit.The second comparing and regulating device receives at its actual valueinput the actual value signal ascertained in response to the forceapplicd'to the chucking head. The rated values may be represented byelectrical signals corresponding to displacement values and/or forcevalues.

I According to a preferred embodiment of the invention, the first ratedvalue supplied to the first comparing regulating means is a forcerepresenting signal and the second rated value is a displacementrepresenting signal supplied to a control input of a limiter.

BRIEF FIGURE DESCRIPTION In order that the invention maybe clearlyunderstood, it will now be described, byway of example, with referenceto the accompanying drawings, wherein:

FIG. 1 is a'block diagram of a first embodiment according to theinvention illustrating the control of a hydraulically operating testingapparatus; and

FIG. 2 illustrates a modification of the apparatus according to FIG. 1,wherein the movable member is displaced to a predetermined position inresponse to breaking of the probe.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS For simplicitys sake, thetesting apparatus is shown schematically in FIGS. 1 and 2.'A testingforce is ap-' plied to the probe 8 by means of a hydraulic cylinder 1which is controlled through a servo valve 2 connecting the cylinder 1 toa source of hydraulic power not shown. The servo valve 2 may becontrolled through a solenoid by electrical signals. A force measuringgauge 4 is arranged between the piston rod of the cylinder 1 and theprobe 8 to be tested. The force measuring gauge may also be arrangedbetween the probe 8 and the frame structure F of the apparatus. Theforce measuring gauge 4 acts as a first sensing device which provides anelectrical signal representing an actual force value.

A second sensing device 3 is arranged for cooperation with the pistonrod to sense the displacement of the piston rod whereby to provide adisplacement rep resenting electrical signal-or value which correspondsto the instantaneous actual position value of the piston rod. Thedisplacement sensing device 3 is connected to an actual input value i ofa first comparing regulating means 12 for supplying theactualdisplacement value signal Si to the comparator 12. Rated valueinput means, for example, a potentiometer 11 is connected to the ratedinput s of the comparator 12 for supplying an adjustable rated signalvalue to the comparator 12. The output of the comparator I2 is connectedto a control or regulating amplifier 13, the output of which in turn isconnected to the input of a limiter stage 14. The limiter stage 14 has acontrol input 10 to which is applied a rated control signal foradjusting the pass range of the limiter to thus adapt the pass range tothe individual requirement.

The output of the limiter 14 is connected through a single pole doublethrow switch 7 which actually may be an electronic switch to the ratedvalue input s of the second comparing regulating device 6. In the shownrest position of the switch 7 the first and second comparing devices areconnected to each other in series fashion. In the actuated dashed lineposition of the switch 7, the rated value inputs of the comparator 6 isconnected with an input terminal 9 to which is applied a force ratedvalue signal Fs. The actual value input i of the comparator or regulator6 is connected to the output of the force sensing device 4 whereby theactual force representing value or signal Pi is applied to the actualvalue input i of the comparator 6.

If there is a difference between the rated and actual value representingsignals applied to the input of the comparator 6, a control signal Y issupplied to the solenoid of the servo valve 2. Thus, this control signalY adjusts the valve 2 in such a manner that equality is establishedbetween the rated and actual signal values supplied to the inputs of thecomparator 6. The circuit arrangement according to FIG. 1 operates asfollows. After the probe 8 has been chucked at one end thereof, thepotentiometer 11 is adjusted to provide the rated value input signal Ssfor the displacement required to also chuck the other end of the probe,that is, the potentiometer 11 is adjusted in accordance with the lengthof the respective probe. Since it may be assumed that the actualdisplacement signal value Si and the rated displacement signal value Ssdo not correspond to each other, a difference voltage will be producedat the output of the comparator or regulator 12. The difference voltageis amplified in the control amplifier 13 and supplied to the input ofthe limiter 14. The limiter, is adjusted through its control input insuch a manner that it passes a voltage corresponding to a force which,when applied to the probe will not result in any damage of the probe orof the chucking heads. The output value of the limiter 14 is thensupplied as a rated force representing signal value Fs to the ratedinput s of the comparator 6. As long as the force measuring gauge 4supplies an actual force representing value Fi O, the piston rod will bedisplaced in response to the rated force value Fs. As soon as the forcesensing gauge 4 provides an actual force value Fi to the actual valueinput i of the second comparator 6, which actual force value correspondsto the rated force value Fs, the adjustment or displacement of thepiston rod is stopped. The probe may now be chucked to the otherchucking head. When the probe is properly chucked at both ends, theswitch 7 is actuated to connect the input terminal 9 to the rated inputof the comparator 6 in order to supply a rated test force signal Fst tothe comparator. Accordingly, the probe 8 is now subjected to the testforce in response to said test force signal.

FIG. 2 illustrates a modified embodiment according to the. invention butemploying the basic circuit elements according to FIG. 1. First, second,third and fourth switching means 22, 28, 29 and 32 are provided. Theseswitching means have a single pole double throw function, however, theymay be represented by electronic switching means'well known in the art.With the aid of these switching means it is possible to switch from thedisplacement movement of the movable chucking head in response to thedisplacement control,

to the adjustment movement of the piston rod to a predetermined positionsubsequent to the breaking of the probe 8. The elements which are thesame in FIGS. 1 and 2 are provided with the same reference numerals. Inthe illustrated full line or rest position of the switching means 22,28, 29 and 32, the actual displacement representing signal Si is appliedthrough the conductor 21 and the switch 22 to the conductor 23 and thusto the actual value input of the comparator 12L Simultaneously, therated value input of the comparator 12 is connected through theconductor 24 and the switch 29 to a rated displacement value supplymeans such as a potentiometer 30 which produces the rated displacementsignal value Ssl. This rated displacement signal value Ssl is adjustableby the potentiometer 30. As in FIG. 1, the comparator 12; is connectedwith its output to the input of a control amplifier 12 which in turn isconnected with its output to a limiter circuit 14.

The limiter circuit 14 has a control input which is connected throughthe conductor 35 and the switch 32 to a potentiometer 34 by means ofwhich a first rated force representing signal Fsl may be adjusted. Theoutput of the limiter 14 is connected through a conductor 25 to therated input of the second comparator control device 6. The force actualvalue input of the comparator 6 is connected to the force sensing gauge4 through the conductor 26, the switch 28 and the conductor 27.

In the actuated or dashed line position of the just mentioned switches,the situation is reversed, in other words, the actual displacementsignal Si is supplied to the comparator 6 and the actual forcerepresenting signal Fi is supplied to the comparator 12. Moreover, therated input of the comparator 12 is connected to the potentiometer 31for adjusting a second rated force value Fs2, while the control input ofthe limiter 14 is connected to a potentiometer 33 for adjusting a seconddisplacement representing rated value signal Ss2.

In the shown rest position of the switch means 22, 28, 29 and 32, thecircuit according to FIG. 2 operates in the same manner as that of FIG.1.

After the probe 8 has been chucked, the switching means 22, 28, 29 and32. are changed into their actu ated or dashed line position whereby theprobe 8 is subjected to a respective force in accordance with apredetermined program. This force may be pre-adjusted by means of thepotentiometer 31 which supplies the rated force value signal Fs2 whichis supplied through conductor 24 to the rated value input of thecomparator 12. As mentioned, the actual value input of the comparator 12is connected to the force sensing gauge 4 through the dashed lineposition of the switch 8 and the conductor 27. Further, the displacementactual value Si is now supplied through the dashed line position of theswitch 22 and the conductors 21 and 26 to the actual value input of thecomparator 6. The control input of the limiter 14 is connected to thesecond rated displacement value Ss2 whereby the potentiometer 33 permitscontrolling the size of the pass range of the limiter l4. Incidentally,the switches 29 and 32 may be ganged as indicated by the dashed line 36and as is well known in the art.

The circuit arrangement according to FIG. 2 operates as follows. Thepotentiometer 33. is adjusted to the second displacement rated value SS2to which the piston rod is to be displaced subsequent to breaking of theprobe 8. The comparator control device 12 monitors the actual forcevalue and the rated force value PS2 so that the former corresponds tothe latter. If a deviation occurs, a control signal Y is producedthrough the control amplifier 13, the limiter l4 and the regulatingcomparator 12 whereby the servo valve 2 is influenced in such a mannerthat the rated force is produced. Normally, the limiting effect of thelimiter 14 does not occur. Similarly, the comparator control device 6has initially no influence on the displacement or adjustment movement.However, as soon as the probe-8 breaks, a large difference occursbetween the rated force value signal Fs2 and the actual force valuesignal Fi at the input of the regulating comparator 12. Accordingly, alarge difference voltage is produced at the output of the comparator 12which is supplied through the control amplifier 13 to the limiter 14which now limits the difference voltage supplied to the input of thecomparator 6 in accordance with the pre-adjusted displacement .ratedvalue Ss2..As long as the rated displacement value does not correspondto the actual displacement value, the piston rod is displaced in thedirection toward achieving the desired value. When the rateddisplacement value and the actual displacement value correspond to eachother, the difference voltage at the output of the regulator 6disappears and accordingly, the movement of the piston rod is stopped.

Although in the example embodiments potentiometers have been shown forestablishing the rated signal values such as the rated displacementsignal value Ssl and the rated force signal value Fsl as well as therespective signals S52 and F52, other signal producing means may beemployed. Moreover, instead of using separate potentiometers as shown,it is possible to use a common potentiometer for the displacement ratedvalues and/or for the force rated values. These voltages may also beproduced by any well known programming unit. Therefore, it is to beunderstood that it is intended to cover all modifications andequivalents within the scope of the appended claims.

What is claimed is:

l. A circuit arrangement for adjusting the position of amovable memberto a predetermined position in accordance with a first rated value,comprising a position control means, first and second sensing means forascertaining respective first and second actual values in response tothe movement of said movable member, first and second comparing means,each having an actual value input and a rated value input, means forconnecting the actual value input of said first comparing means to oneof said sensing means and the actual value input ofthe second comparingmeans to the other sensing means, first rated value producing meansconnected to the rated value input means of the first comparing means,said first comparing means having an output connected to the rated valueinput of the second comparing means whereby a second rated value isapplied to the rated value input of the second comparing means, thelatter having an output connected to said position control means, saidfirst comparing means comprising a comparator and a limiter stageconnected between the comparator and the rated value input of the secondcomparing means, said limiter stage comprising a control input forreceiving a rated control signal which determines the pass range of thelimiter stage, whereby the controlled movement of the movable member inaccordance with a rated value is stopped when the second actual valuereaches or exceeds the second rated value, a rated value terminal, andswitch means having a rest position connecting the rated value input ofthe second comparing means to an output of the first comparing means andan actuated position connecting said rated value terminal to the ratedvalue input of said second comparing means.

- 2. A circuit arrangement for adjusting the position of a movablemember to a prcdetermined'position in aecordance with a first ratedvalue, comprising a position control means, first and second sensingmeans for ascertaining respective first and second actual values inresponse to the movement of said movable member, first and secondcomparing means, each having an actual value input and a rated valueinput, means for connecting the actual value input of said firstcomparing means to one of said sensing means and the actual value inputof the second comparing means to the other sensing means, first ratedvalue producing means connected to the rated value input means of thefirst comparing means, said first comparing means having an outputconnected to the rated value input of the second comparing means wherebya second rated value is applied to the rated value input of the secondcomparing means, the latter having an output'connected to said positioncontrol means, whereby the controlled movement of the movable-memberinaccordance with a rated value is stopped when the second actual valuereaches or exceeds the second rated value, a limiter connected betweensaid first and second comparing means and including a control input,first, second, third and fourth switch means each having a rest positionand an actuated position, said first switch means connecting in its restposition said first actual value sensing means to the actual value inputof the first comparing means and in its actuated position to the actualvalue input of the second comparing means, said second switch meansconnecting in its rest position said second actual value sensing meansto the actual value input of the second comparing means and in itsactuated position to the actual value input of the first comparingmeans, means for supplying first and second force representing ratedvalues, means for supplying first and second displacement representingrated values, said third switch means connecting to the rated valueinput of the first comparing means in its rest position the first rateddisplacement value and in its actuated position the second rated forcevalue, said fourth switch means connecting to the limiter control inputin its rest position the first rated force value and in its actuatedposition the second rated displacement value.

3. The circuit arrangement according to claim 2, fur ther comprisingmeans for ganging said third and fourth switch means. I

4. A circuit arrangement for adjusting the position of a movable memberto a predetermined position in accordance with a first rated valuecorresponding to the displacements of said movable member, comprising aposition control means, first and second sensing means for ascertainingdisplacement and force representing actual values respectively inresponse to the movement of said movable member, first and secondcomparing means each having an actual value input and a rated valueinput, means for connecting the actual value input of said firstcomparing means to said displace ment sensing means and the actual valueinput of the second comparing means to said force sensing means,displacement rated value producing means connected prising a controlinput for receiving a rated control signal which determines the passrange of the limiter stage, whereby the controlled movement of themovable member in accordance with a rated value is stopped when saidforce actual value reaches or ex ceeds said second rated value.

5. The circuit arrangement according to claim 4, wherein said movablemember is a chucking head in a hydraulically operated material testingapparatus.

1. A circuit arrangement for adjusting the position of a movable memberto a predetermined position in accordance with a first rated value,comprising a position control means, first and second sensing means forascertaining respective first and second actual values in response tothe movement of said movable member, first and second comparing means,each having an actual value input and a rated value input, means forconnecting the actual value input of said first comparing means to oneof said sensing means and the actual value input of the second comparingmeans to the other sensing means, first rated value producing meansconnected to the rated value input means of the first comparing means,said first comparing means having an output connected to the rated valueinput of the second comparing means whereby a second rated value isapplied to the rated value input of the second comparing means, thelatter having an output connected to said position control means, saidfirst comparing means comprising a comparator and a limiter stageconnected between the comparator and the rated value input of the secondcomparing means, said limiter stage comprising a control input forreceiving a rated control signal which determines the pass range of thelimiter stage, whereby the controlled movement of the movable member inaccordance with a rated value is stopped when the second actual valuereaches or exceeds the second rated value, a rated value terminal, andswitch means having a rest position connecting the rated value input ofthe second comparing means to an output of the first comparing means andan actuated position connecting said rated value terminal to the ratedvalue input of said second comparing means.
 2. A circuit arrangement foradjusting the position of a movable member to a predetermined positionin accordance with a first rated value, comprising a position controlmeans, first and second sensing means for ascertaining respective firstand second actual values in response to the movement of said movablemember, first and second comparing means, each having an actual valueinput and a rated value input, means for connecting the actual valueinput of said first comparing means to one of said sensing means and theactual value input of the second comparing means to the other sensingmeans, first rated value producing means connected to the rated valueinput means of the first comparing means, said first comparing meanshaving an output connected to the rated value input of the secondcomparing means whereby a second rated value is applied to the ratedvalue input of the second comparing means, the latter having an outputconnected to said position control means, whereby the controlledmovement of the movable member in accordance with a rated value isstopped when the second actual value reaches or exceeds the second ratedvalue, a limiter connected between said first and second comparing meansand including a control input, first, second, third and fourth switchmeans each having a rest position and an actuated position, said firstswitch means connecting in its rest position said first actual valuesensing means to tHe actual value input of the first comparing means andin its actuated position to the actual value input of the secondcomparing means, said second switch means connecting in its restposition said second actual value sensing means to the actual valueinput of the second comparing means and in its actuated position to theactual value input of the first comparing means, means for supplyingfirst and second force representing rated values, means for supplyingfirst and second displacement representing rated values, said thirdswitch means connecting to the rated value input of the first comparingmeans in its rest position the first rated displacement value and in itsactuated position the second rated force value, said fourth switch meansconnecting to the limiter control input in its rest position the firstrated force value and in its actuated position the second rateddisplacement value.
 3. The circuit arrangement according to claim 2,further comprising means for ganging said third and fourth switch means.4. A circuit arrangement for adjusting the position of a movable memberto a predetermined position in accordance with a first rated valuecorresponding to the displacements of said movable member, comprising aposition control means, first and second sensing means for ascertainingdisplacement and force representing actual values respectively inresponse to the movement of said movable member, first and secondcomparing means each having an actual value input and a rated valueinput, means for connecting the actual value input of said firstcomparing means to said displacement sensing means and the actual valueinput of the second comparing means to said force sensing means,displacement rated value producing means connected to the rated valueinput means of the first comparing means, said first comparing meanshaving an output connected to the rated value input of the secondcomparing means whereby a second rated value is applied to the ratedvalue input of the second comparing means, the latter having an outputconnected to said position control means, said first comparing meanscomprising a comparator and a limiter stage connected between thecomparator and the rated value input of the second comparing means, saidlimiter stage comprising a control input for receiving a rated controlsignal which determines the pass range of the limiter stage, whereby thecontrolled movement of the movable member in accordance with a ratedvalue is stopped when said force actual value reaches or exceeds saidsecond rated value.
 5. The circuit arrangement according to claim 4,wherein said movable member is a chucking head in a hydraulicallyoperated material testing apparatus.